Thanks for the detailed answer, Bill. However, it bring up another question... :o] *I can't help but smirk as I visualize you glancing heavenward*
How do I know when the stigma is producing stigmatic fluid?
The short answer is yes. It is however, more important that the stigma be
producing stigmatic fluid at the time the pollen is being applied and precautions be taken to retard rain from dripping into the crevice between the lips at the time the pollen is being applied and it is not water logged to the point it is holding water.
I do not know the precise reduction in pollen strikes for iris blooms pollinated under these conditions. It does appear to be reduced. I do know that pollen strikes are possible and probable regardless.
In daylilies, the number of pollen strikes is only slightly reduced (about 15%) in periods of intermittent, gentle rain so long as the stigma is receptive (producing fluid).